/*
 * http://code.google.com/p/simple-lexing-parsers-4-scala/
 * 
 * Copyright (c) 2011, Sanjay Dasgupta
 * All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 * 
 *     * Redistributions of source code must retain the above copyright
 *       notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above copyright
 *       notice, this list of conditions and the following disclaimer in the
 *       documentation and/or other materials provided with the distribution.
 *     * The name of the author may not be used to endorse or promote products
 *       derived from this software without specific prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL <COPYRIGHT HOLDER> BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

package slp

import java.util.regex.Pattern

private[slp] class Lexer (tokens: Array[String]) {
  def lex(s: String, offset: Int) = {
    val matchesByLength = tokenPatterns.map(pi => {
        val m = (pi._1).matcher(s.subSequence(offset, s.length))
        if (m.lookingAt) {
          (m.group, pi._2)
        } else {
          (null, 0)
        }
      }).seq.filter(_._1 ne null).sortWith((a, b) => {a._1.length > b._1.length});
    if (matchesByLength.isEmpty) {
      (null, 0)
    } else {
      val maxLength = matchesByLength.head._1.length;
      val byLengthAndPriority = matchesByLength.takeWhile(_._1.length == maxLength).sortWith((a, b) => {a._2 < b._2})
      byLengthAndPriority.head
    }
  }
  private val tokenPatterns = tokens.par.map(Pattern.compile(_, (Pattern.MULTILINE | Pattern.DOTALL))).zipWithIndex
}
